I'm running the custom tab on Microsoft Teams app. It correctly works on Desktop (client and browser) and iPhone client, but it doesn't work on the Android mobile MS Teams app. Web page with the app is opening correctly in Chrome for Android. Tested on Samsung S22 and A53.
When inspecting the page in chrome://inspect/#devices there is no error just Untitled page and no network activity. I was also checking the logs of the web server were the app is hosted but there is no activity.
Since app is hosted on a docker container in Azure VM I've tried to open firewall to the whole Internet but it hadn't helped.
Updated @microsoft/teams-js to 2.13.0 - hasn't helped as well
Checked manifest file. Valid domains and other info is correct.
It turned out to be problem with certificate
openssl s_client -showcerts -connect some.domain.com:443
was showing verification errors. After changing the certificate problem is gone.